Questions tagged [web3js]

Javascript API and library for Ethereum
To develop applications on Ethereum, you can use the web3 object provided by the web3.js library. Under the hood it communicates to a local node through RPC calls. web3.js works with any Ethereum node, which exposes an RPC layer.
https://github.com/ethereum/wiki/wiki/JavaScript-API

What is the difference between a transaction and a call? In some interfaces, I can interact with contracts via calls or via transactions. What is the difference between the two, and can contracts also ...

Take an example of a voting DApp. A user clicks on a vote button, then behind the scenes a transaction gets mined on the blockchain, and finally the DApp tells the user their vote has been recorded.
...

This may be a very basic question, I don't know why but I am unable to find correct solution to how can I call my contract's method using sendTransaction. I have a transfer(address, uint256) function ...

I want to create and sign a transaction in browser using web3. In order to create a raw transaction, I think I have to do something like this (hopefully you can fill the gaps of my knowledge)
var pk =...

It seems that the purpose of function foo() constant {} is to indicate that a function does not change the contract's state. And yet, as it states here, the compiler doesn't actually enforce this. So ...

In Solidity (0.3.2) I am aware that there is no way to throw specific exceptions. (Everything is an invalid JUMP error.) It seems beneficial to have a way to log specific errors. Does it make sense to ...

I am storing data in my contract using a mapping of structs.
For examples sake, say I'm storing employee info (name/address/salary), mapped by their employee ID.
Via a web front-end, I'd like to be ...

I would like to explore the storage data of a contract. I have geth fully synched and I interact with it over RPC. There is the function "eth.getStorageAt(addr, index, block)" provided, but you need ...

I would like to reliably induce a fork on a private testnet so that I can test the behavior of off-blockchain code that interacts with contracts. (see related questions as to why I would want to do ...

I'm trying to create and deploy a smart contract through NodeJS using web3, but it is not working as I get a "web3.eth.contract.new is not a function". Here is my code:
var web3 = require('ethereum....

I have an ABI and the input value of the transaction and want to know what function has been called on a contract and with what arguments (one or multiple of different types), preferably using geth, ...

So Metamask allows in it UI to connect to different ethereum nw (public/ testnet) right.
Do who is maintaining these peers?
Can I trust these peers?.
If so, can I setup similar service on my machine ...